The proposed research project continues work on the development and validation of psychometric instruments designed to quantitatively measure vision disability in low vision patients. Progress in the previous project period includes validation with Rasch analysis of self-assessment questionnaires that ask subjects to rate the difficulty of performing specific activities. These studies demonstrated that: 1) all such questionnaires measure the same visual ability construct, 2) visual ability has a two-dimensional structure with reading tasks loading heavily onto one dimension and mobility tasks loading heavily onto the other dimension, 3) one dimension of visual ability is central vision (the principal component of log visual acuity and log contrast sensitivity) and the second dimension most likely is related to some attribute of visual fields, 4) co-morbidities have minor confounding effects on visual ability measurements, 5) instruments designed to assess functional vision have the same calibration for different diagnostic categories, and 6) the effects of low vision rehabilitation are manifested as item-specific changes in difficulty, rather than as person-specific changes in visual ability. The presently proposed project has four specific aims: 1) determine the relationship between functional vision measures based on self-assessments and task performance measures, 2) determine the relationship between visual ability and attributes of peripheral and central visual field loss, 3) determine the responsiveness of visual ability and functional vision measures to low vision rehabilitation, and 4) develop and validate methods of measuring the value of low vision rehabilitation outcomes. To achieve Aim 1, we will perform measures reading speed versus character size, walking speed and obstacle avoidance, face discrimination, visual search, tracing speed and accuracy, and accuracy of a manipulative task. To achieve Aim 2, we will obtain kinetic and static peripheral visual field measures and static central visual field measures on different groups of patients. To achieve Aim 3, we will obtain subject difficulty ratings to Goals and Tasks in our Activity Inventory before and after low vision rehabilitation. And, to achieve Aim 4, we will use triadic comparison and willingness-to-pay methods of measuring the values of alternative low vision rehabilitation outcomes.